Importing OBJ File to the center with correct orientation
If the object is already in the scene, select it. In the 3D viewport, open the transform panel (little cross on the right). You will see the location. Click on X, Y and Z and change their values to 0, this should put the object at the center of the scene.

Here is a picture where you can see which fields you need to change. You can then change the Rotation to give it the desired orientation.


For the orientation, you can also choose it when you import the OBJ file. When you do File -> Import -> Wavefront, you will be given the choice for the forward and up axes of the object :